No, the "Custom Text ... " option is for custom "static" text only, no parameters, no options.
To display the selection mode text (related to the mode number) for selector that was already assigned as button, switch, rotary switch before for your display:
1. Click on the "Selector_#" in the parameter table (section "SimVim Functions"
2. Select the "7-Seg Display: TEXT" option
3. Select the 7-segment display (that has to be assigned already)
4. In the options window add the text, and shift position, and value (mode number ) for this text